396 THE yOYAGE OF H.M.S. CHALLENGER. 



and the second. Lateral walls armed with a long tooth over the anterior portion of the 

 branchial region. 



Pleon with the three anterior somites smooth and subequal ; the fourth and fifth of 

 equal length, but dorsally elevated posteriorly, and each bearing a slender tooth. The 

 sixth somite is as long as the three preceding combined, but not so deep, and is armed at 

 the postero-dorsal margin with a long, slender tooth, and a small point exists at the 

 postero -inferior lateral angles. 



Telson long and slender, half the length of the sixth somite, and terminating in 

 a sharply pointed fork, flanked by two small teeth. 



Ophthalmopoda clavate, about two-thirds the length of the carapace, or a little 

 longer than the first joint of the first pair of antennae. 



First pair of antennas having the first joint of the peduncle broad at the base to 

 receive the otocyst, and armed with a strong tooth on the outer margin ; the second and 

 third joints are subequal, and together of about the same length as the first ; the third 

 supporting one long and one short flagellum ; the longer is about half the length of the 

 animal, and the smaller about the length of the terminal joint of the peduncle. 



The second pair of antennas has a sharp tooth on the outer distal angle of the 

 penultimate joint of the peduncle, and the terminal joint is about two-thirds the length 

 of the ophthalmopoda (the flagellum is lost). Scaphocerite as long as the peduncle of 

 the first pair of antennas, armed on the outer margin, near the apex, with a strong tooth, 

 and fringed on the inner margin with a series of hairs. 



The first pair of gnathopoda is generic in appearance, and terminates in a small, flat, 

 ovate, spatuliform joint. 



The second pair is very long and slender, and terminates in a few long and strong hairs. 



The first pair of pereiopoda is simple, the second and third long and chelate, and the 

 fourth and fifth rudimentary. 



Pleopoda long and slender, slightly shortening posteriorly ; ultimate pair with a 

 strong tooth at the outer distal angle of the basal joint ; the inner branch as long again 

 as the telson, the outer about one-fifth longer than the inner, and armed with a tooth on 

 the outer margin, about two-fifths distant from the extremity, the intervening space to 

 the apex being concave and fringed with hairs, as is also the inner margin. 



Length, 8 mm. (0'33 in.). 



Habitat. — South of Australia, March 1874. One specimen. 



Observations. — This species was taken associated with Sergestcs dorsisjrinalis, from 

 which it materially differs in having no tooth on the dorsal median surface, but one of great 

 length on each side, on the lateral walls of the carapace, just above the apophysis of the 

 mandibles ; and in having a tooth at the dorsal extremity of the three posterior somites 

 of the pleon. 



